Methodology for airflow rate measurements in a naturally ventilated mock-up animal building with side and ridge vents

摘要

Currently there exists no generally accepted reference technique to measure the ventilation rate through naturally ventilated (NV) vents. This has an impact on the reliability of airflow rate control techniques and emission rate measurements in NV animal houses. As an attempt to address this issue a NV test facility was built to develop new airflow rate measurement techniques for both side wall and ridge vents. Three set-ups were used that differed in vent configuration, i.e. one cross ventilated set-up and two ridge ventilated set-ups with different vent sizes.The airflow through the side vents was measured with a technique based on an automatic traverse movement of a 3D ultrasonic anemometer. In the ridge, 7 static 2D ultrasonic anemometers were installed. The methods were validated by applying the air mass conservation principle, i.e. the inflow rates must equal the outflow rates.The calculated in - and outflow rates agreed within (5 +/- 8)%, (8 +/- 5)% and (-9 +/- 7)% for the three different set-ups respectively, over a large range of wind incidence angles. It was found that the side vent configuration was of large importance for the distribution of the airflow rates through the vents. The ridge proved to be a constant outlet, whilst side vents could change from outlet to inlet depending on the wind incidence angle. The range of wind incidence angles in which this transition occurred could be clearly visualized.